The MagickWand interface is a new high-level C API interface to ImageMagick core methods. We discourage the use of the core methods and encourage the use of this API instead. Post MagickWand questions, bug reports, and suggestions to this forum.

I'd suggest you first try modifying one of your images using the IM command line. Anthony has several sections about this kind of operation. For example, see the four subsections which start withSepia Tone
and then the whole section here:Recoloring Images with Lookup Tables

Try those methods and if you find a technique that gives you what you want, then you can look at converting the command line into MagickWand code. Whether you will need to iterate over all the pixels depends upon what method is required to achieve the result you want.

Pete

Sorry, my ISP shutdown all personal webspace so my MagickWand Examples in C is offline.
See my message in this topic for a link to a zip of all the files.